Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1999-06-01
2001-07-24
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S198000
Reexamination Certificate
active
06265523
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to processes for producing an aromatic/aliphatic copolycarbonate having impact resistance, a low photoelastic coefficient, a high refractive index, a high Abbe's number, excellent transparency, and excellent heat resistance. More particularly, this invention relates to processes for producing an aromatic/aliphatic copolycarbonate having an excellent color tone.
BACKGROUND OF THE INVENTION
Polycarbonate resins obtained by the interfacial polymerization of one or more aromatic dihydroxy compounds, e.g, bisphenol A, with phosgene in the presence of a proton acceptor are used as optical materials in applications such as various lenses, prisms, and optical-disk substrates because these resins are excellent not only in mechanical properties including impact resistance but in heat resistance and transparency.
However, the polycarbonate produced from bisphenol A as only the aromatic dihydroxy compound has the following drawbacks.
Since the polycarbonate has a high photoelastic coefficient and relatively poor melt flowability, it gives molded articles having enhanced birefringence and an Abbe's number as low as 30 although the refractive index thereof is high, i.e., 1.58. Namely, the performances of the polycarbonate are insufficient for wide use in applications such as photo-recording materials and optical lenses.
For the purpose of eliminating the above drawbacks of bisphenol A polycarbonate, the present inventors previously proposed an aromatic/aliphatic copolycarbonate resin (JP-A-10-120777; the term “JP-A” used herein means an unexaminied and published Japanese patent application). This aromatic/aliphatic copolycarbonate resin has excellent impact resistance and heat resistance, a low photoelastic coefficient, and a high Abbe's number and can hence be extensively used as an optical material. For producing such an aromatic/aliphatic copolycarbonate, the method known as a transesterification process is advantageously used because it is difficult to produce the polymer by the ordinary phosgene process. In the transesterification process, an aromatic dihydroxy compound, an aliphatic dihydroxy compound, and a carbonic diester, e.g., diphenyl carbonate, are subjected in a molten state to polycondensation through transesterification reactions.
In the transesterification reaction for polycarbonate production, polycondensation is usually conducted while heating the reaction mixture at a temperature of from 200 to 330° C. The polymer being yielded is thus exposed to such a high temperature for a prolonged time period. Because of this heat history, the polymer yielded has an impaired color tone and other deteriorations. Namely, the prior art process has a drawback that a polymer of excellent quality is difficult to obtain. Consequently, the polycarbonate obtained by the transesterification process is unsuitable for use in fields where a satisfactory color tone is required.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the above-described problems accompanying prior art techniques.
Accordingly, an object of the present invention is to provide process for producing an aromatic/aliphatic copolycarbonate having excellent impact resistance, excellent heat resistance, a high Abbe's number, a low photoelastic coefficient, and an excellent color tone.
The copolycarbonate resin obtained by the process of the present invention comprises constituent units derived from an aromatic dihydroxy compound represented by the following formula (1), constituent units derived from an aliphatic dihydroxy compound represented by the following formula (2), and constituent units derived from a carbonic diester.
(In formula (1), X is
wherein R
3
and R
4
each is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group, or R
3
and R
4
may be bonded to each other to form a ring; R
1
and R
2
may be the same or different and each is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a halogen atom; and m and n, which each indicates the number of substituents, each is an integer of 0 to 4.)
(In formula (2), R
5
, R
6
, R
7
, and R
8
each is a hydrogen atom or a univalent alkyl group having 1 to 10 carbon atoms.)
The present inventors made intensive studies in order to accomplish the above object. As a result, they have found that the color tone of an aromatic/aliphatic copolycarbonate has a correlation with the nitrogen content, iron content, aldehyde group and/or formyl group content, free-chlorine content of the aliphatic dihydroxy compound used or a melt Hazen unit of the aliphatic dihydroxy compound which has been maintained at a specific temperature for a specific time period. It has also been found that a resin having a satisfactory color tone is obtained by using such a specific aliphatic dihydroxy compound. The present invention has been completed based on those findings.
According to a first embodiment of the present invention, there is provided a process for producing an aromatic/aliphatic copolycarbonate which has a nitrogen content of 9 ppm or lower, which comprises subjecting an aromatic dihydroxy compound represented by the formula (1) described above, an aliphatic dihydroxy compound represented by the formula (2) described above, and a carbonic diester to polycondensation under heating and melting, wherein the aliphatic dihydroxy compound having a nitrogen content of 10 ppm or lower is used.
According to a second embodiment of the present invention, there is provided a process for producing an aromatic/aliphatic copolycarbonate, which comprises subjecting an aromatic dihydroxy compound represented by the formula (1), an aliphatic dihydroxy compound represented by the formula (2), and the carbonic diester to polycondensation under heating and melting, wherein the aliphatic dihydroxy compound having an iron content of 1 ppm or lower, preferably 0.5 ppm or lower, and more preferably 0.2 ppm or lower, is used.
According to a third embodiment of the present invention, there is provided a process for producing an aromatic/aliphatic copolycarbonate, which comprises subjecting an aromatic dihydroxy compound represented by the formula (1), an aliphatic dihydroxy compound represented by the formula (2), and the carbonic diester to polycondensation under heating and melting, wherein the aliphatic dihydroxy compound having a content of aldehyde groups and/or formyl groups of 100 ppm or lower is used.
According to a fourth embodiment of the present invention, there is provided a process for producing an aromatic/aliphatic copolycarbonate, which comprises subjecting an aromatic dihydroxy compound represented by the formula (1), an aliphatic dihydroxy compound represented by the formula (2), and the carbonic diester to polycondensation under heating and melting, the aliphatic dihydroxy compound having a content of free chlorine of 5 ppm or lower is used.
According to a fifth embodiment of the present invention, there is provided a process for producing an aromatic/aliphatic copolycarbonate, which comprises subjecting an aromatic dihydroxy compound represented by the formula (1), an aliphatic dihydroxy compound represented by the formula (2), and the carbonic diester to polycondensation under heating and melting, the aliphatic dihydroxy compound which has a melt Hazen unit of 40 or smaller, preferably 20 or smaller, and more preferably 15 or smaller, after having been maintained at 260° C. for 5 hours in the air is used.
DETAILED DESCRIPTION OF THE INVENTION
The processes for producing an aromatic/aliphatic copolycarbonate according to the present invention will be explained in detail below.
The copolycarbonate obtained by process of the present invention comprises constituent units derived from an aromatic dihydroxy compound represented by the formula (1) described above, constituent units derived from an aliphatic dihydroxy compound represented by the formula (2) described above, and constituent units derived from a carbonic diester.
Examples of the aromatic dihydroxy compound wh
Fujimori Takayasu
Kondo Osamu
Konishi Takashi
Nagai Satoshi
Sasaki Makoto
Boykin Terressa M.
Mitsubishi Gas Chemical Company Inc.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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